Causes of stomach cancer
The exact causes of cancer of the stomach are still unknown, although research is being done to try to find the cause. Over the past 30 years the number of people who develop stomach cancer has fallen, especially in Western countries. Although the reason for this is unknown, it is thought to be related to changes in our diet, particularly the use of refrigeration, which has meant that people eat more fresh food and less smoked and pickled food.
Cancer of the stomach is more common in men, particularly in their 60s and 70s. Factors that can increase the risk of stomach cancer include:
pernicious anaemia, which affects the lining of the stomach and results in a lack of vitamin B12.
atrophic gastritis – a stomach disorder
helicobacter pylori (H pylori) – an infection that affects the stomach
a hereditary condition in which people have small growths (polyps) in their stomach
Barrett's oesophagus – a condition where abnormal cells develop in the lining of the lower end of the gullet or the place where the gullett joins the stomach (the gasto-oesophageal junction). It is not a cancer, but over a long period of time a small number of people with this condition may develop cancer of the gullet or stomach.
Symptoms of stomach cancer
The symptoms of stomach cancer may include any of the following:
indigestion that does not go away
losing your appetite
difficulty in swallowing losing weight
a bloated feeling after eating
feeling sick (nausea) or being sick (vomiting)
blood in the stools (bowel motion) or black stools
tiredness due to anaemia (from bleeding from the wall of the stomach)
Many of the symptoms described above are common to conditions other than cancer of the stomach. Most people who see their doctor with these symptoms will not have cancer. However, it is important to have them checked so that further tests can be done if necessary.
How stomach cancer is diagnosed
Usually you begin by seeing your family doctor (GP), who will examine you and arrange any tests or x-rays that may be necessary. Your GP will refer you to hospital for these tests and for specialist advice and treatment.
The doctor at the hospital will take your full medical history before doing a physical examination. You will probably have a blood test taken to check your general health. You may also be asked to bring a stool sample with you so that it can be tested for blood.
To examine the stomach in more detail, your doctor may arrange for you to have an endoscopy or a barium meal. Some people may have just one test while others may have both.
Endoscopy/ Endoscopic ultrasound
This is the most common test used to diagnose cancer of the stomach. Before an endoscopy the stomach has to be empty, so you will be asked not to eat or drink anything for at least four hours beforehand. Most people are given a sedative before an endoscopy. The sedative is usually given as an injection into a vein in your arm. This will make you feel sleepy so you don't feel too uncomfortable during the test. A local anaesthetic may also be sprayed onto the back of your throat and the doctor or nurse passes an endoscope (a thin, flexible tube) down the gullet into the stomach.
The endoscope has a light and camera at the end. Photographs are taken of the lining of the stomach and a small sample of cells (biopsy) is taken for examination under a microscope.
Sometimes the endoscopy tube has an ultrasound probe at the end, which allows an ultrasound scan to be done of the stomach and surrounding structures. This is known as an endoscopic ultrasound.
An endoscopy can be uncomfortable but it is not painful. After a few hours the effects of the sedative should have worn off. You will then be able to go home. You should not drive for several hours afterwards and it is advisable to arrange for someone to either drive you home or travel home with you. Some people have a sore throat after their endoscopy. This is normal and should disappear after a few days.
This test will be done in the hospital x-ray department. You will be asked not to eat or drink anything for at least six hours before the test. You will then be given a white, chalky-tasting liquid to drink. This contains barium, which makes the gullet and stomach show up on an x-ray.
You'll be asked to lie on a couch, and the doctor will watch on the x-ray screen as the barium passes through your stomach. To get a clear picture, the room will be darkened during the test. The couch will be tipped in several different positions to allow the barium to flow through the stomach. A barium meal test usually takes less than an hour and may be slightly uncomfortable. The doctor, and often a nurse, will be in the room with you and will be able to answer any questions you may have.
Most people feel fine after the test, but it may be a good idea for a relative or friend to travel home with you. Sometimes the barium causes constipation so you may need to take a laxative for a couple of days. Your stools are likely to be very pale for a few days.
Further tests for stomach cancer
If the tests show that you do have cancer of the stomach, your doctor may want to do some more tests to see if the cancer has spread outside the stomach or to other parts of the body.
CT (computerised tomography) scan
A CT scanner takes a series of x-rays which build up a three-dimensional picture of the inside of the body. The scan is painless but takes longer than an x-ray (10–30 minutes). It may be used to find exactly where the tumour is, or to check for any spread of the disease.
A CT scan
Most people who have a CT scan are given a drink or injection to allow particular areas to be seen more clearly. For a few minutes this may make you feel hot all over. Before having the injection or drink, it is important to tell your doctor and the person doing the scan if you are allergic to iodine or have asthma. If you are allergic or have asthma you may need to have steroids on the day before and the day of the scan. You will probably be able to go home as soon as the scan is over.
Ultrasound measures the size and position of a tumour and is done in the hospital scanning department. It is painless and only takes a few minutes.
Once you are lying comfortably on your back, a gel is spread onto your abdomen. A small device which produces sound waves is then passed over the area. The sound waves make up a picture of the stomach and liver, which can be seen on a computer screen.
Staging and grading of stomach cancer
The stage of a cancer is a term used to describe its size and whether it has spread beyond its original site. Knowing the extent of the cancer helps the doctors to decide on the most appropriate treatment.
A commonly used staging system is described below. You may find it helpful to refer to our diagram of the stomach wall when reading this booklet:
Stage 1A The cancer is contained within the inner lining of the stomach (mucosa) only.
Stage 1B The cancer has spread through the mucosal layer of the stomach either to the muscle layer, OR it is affecting up to six of the nearby lymph nodes.
Stage 2 The cancer has spread through the mucosa and is affecting between seven and 15 lymph nodes nearby, OR it is affecting the muscle layer and up to six lymph nodes, OR it has spread to the outer layer of the stomach (serosa).
Stage 3A The cancer has spread to the muscle layer of the stomach and also to between seven and 15 lymph nodes nearby, OR it has spread to the outer layer of the stomach and is affecting up to six lymph nodes, OR it has spread to structures close to the stomach but not to any lymph nodes or any other parts of the body.
Stage 3B The cancer has spread to the serosa and it is also affecting between seven and 15 lymph nodes.
Stage 4 The cancer has spread to organs close to the stomach and to at least one lymph node, OR to more than 15 lymph nodes, OR it has spread to other parts of the body such as the lungs. This is known as secondary cancer (or metastatic cancer).
If the cancer comes back after initial treatment it is known as recurrent stomach cancer.
The grade of a cancer gives an idea of how quickly it may develop. To find the grade of your cancer, your doctors will look at a sample of the cancer (a biopsy) under the microscope. The cancer will be graded as:
Grade 1 (low grade) – the cancer cells tend to be slow growing, look quite similar to normal cells (are 'well differentiated') and are less likely to spread.
Grade 2 (moderate grade) – the cells look more abnormal.
Grade 3 (high grade) – the cancer cells tend to be more quickly growing, look very abnormal (are 'poorly differentiated') and are more likely to spread than low- grade cancers.